1. Field of the Invention
The present invention relates to an electronic instrument which provides a resettable security code for preventing burglary and a method for rewriting the security code.
2. Background of the Invention
Of the electronic instruments powered by a battery, such as a car stereo unit, some have conventionally provided a security code set therefor. For example, consider that a thief mounts his stolen instrument in his own car. In this case, the stolen device requires him to input the same security code. Hence, if no match takes place between the security code pre-set in the instrument itself and the inputted security code, the thief cannot use the stolen device.
These kinds of electronic instruments are not operated until the preset security code is entered. This serves to prevent burglary.
The security code is thus required to be strictly protected. Actually, a correspondence table between the serial number of each instrument and the relevant security code is safekept in the manufacturer company or the service center of the company located closer to the user. The security code is distributed to the user as a label.
When the user mounts the electronic instrument to a car, for example, the user is required to enter the distributed security code for starting the instrument.
By the way, the correspondence table on which the security code is described is safekept in the manufacturer company or its branch office or distributed to the user as a lable. This is unfavorable to the security of the code. That is, if the user pastes the distributed label on the electronic instrument, another person can easily get the security code.
Even if another person gets the security code of the user, conventionally, the user cannot change the security code preset when manufacturing the electronic instrument. To avoid this disadvantage, for example, if the electronic instrument is arranged so that the user himself can reset the security code, then the initializing method for resetting the security code has to be made public, which leads to lowering the security level.
Under these circumstances, the present invention is made for overcoming the foregoing shortcomings. It is an object of the present invention to provide an electronic instrument which provides simplified means for managing the security code and a capability of setting the security code and a method for rewriting the security code.